The present disclosure relates generally to the field of brightness and/or contrast control in display systems. More particularly, the present disclosure relates to optimization of the brightness and/or contrast of a display.
Displays are utilized in a wide variety of applications including but not limited to medical, military, avionic, entertainment and computing applications. In one exemplary application, displays are used in head-up display (HUD) systems and wearable displays, such as, helmet mounted display (HMD) systems. In aircraft applications, HUD and HMD systems advantageously allow the flight crew to maintain eye contact with the outside environment while simultaneously viewing information from aircraft systems and sensors in a graphical and alphanumeric format overlaying the outside world view. Head-up display systems are known to provide conformal information such that displayed features overlay the environmental view or display information from a camera or other imaging sensor (such as a visible light imaging sensor, infrared imaging sensor, millimeter wave radar imager, etc.) mounted on the aircraft.
For displayed video, a constant video contrast is not sufficient for displaying all video information while important incoming video content such as runway lighting is mapped to peak display brightness. Some conventional HUD systems provide two knobs that control video brightness and video contrast independently. Such video display control may not be optimal for all situations. For example, when enhanced vision images are used in the HUD system during low visibility approaches, video contrast and brightness need to be adjusted by the pilot such that the emerging sensed scene is displayed in a manner that clearly displays and distinguishes illuminated runway lights.
Under such conditions, the displayed image should be set to a maximum contrast and brightness ensuring that objects with a high degree of illumination such as runway lights are displayed with optimal pixel intensity while objects with a lesser degree of illumination such as fog are displayed with a lesser degree of pixel intensity. With a conventional two knob solution, this configuration results in both knobs being turned to full deflection. If a user such as a pilot desires to increase the average video brightness to bring more terrain data into view, the contrast knob may have to be adjusted so that the contrast is lower. Accordingly, a two knob system in many cases requires a non-intuitive combination of separate brightness and contrast control signals to achieve an optimum output display that may result in a prolonged period of user adjustment to both knobs. Prolonged user adjustments to a user interface during a critical phase of flight such as landing can lead to pilot error. Accordingly, there is a need for a system and method of providing an optimal degree of brightness and/or contrast with minimal adjustments from a user. There is also a need for a systems and methods of providing an optimal degree of brightness and contrast with minimal adjustments from a user. There is a further need for systems for and methods of controlling brightness and/or contrast without requiring a two knob interface. There is still a further need for systems for and methods of controlling brightness and contrast with a less complex user interface.
Furthermore, in many display applications, such as, in HUD systems for aircraft or land based vehicles or in medical imaging systems, text, lines, numbers or other symbology is often superimposed on video content being displayed. In the context of aircraft, the information displayed is typically data and/or symbolic images indicative of flight conditions such as altitude or airspeed and may also represent other information such as navigation or guidance information. The pixel intensity of symbology that is superimposed on video content is conventionally at maximum pixel intensity at all times. Further, the brightness of the display for both symbology and video content is typically controlled by a common backlighting system. However, in some cases it is desirable for symbology to be displayed at less than maximum brightness without having to turn down the common backlighting system. This is because turning down the common backlighting system can drop video content of objects (e.g. terrain) below a viewable threshold. Accordingly, there is a need for a system for and a method of providing a variable symbology brightness so that a user is able to clearly view video content while also altering the level of symbology brightness.